The above-referenced '822 application and '507 patent, both of which being incorporated by reference herein in their respective entireties, disclose embodiments of an oscillating sander having a combined motor and mechanical drive for transmitting rotational and reciprocating motion to an output motor shaft. The output motor shaft extends upward through a worktable, and in one embodiment is adapted to accept a drum-sander-type sanding spindle assembly thereon. When the sanding spindle assembly is coupled to said output motor shaft and the motor and mechanical drive system is turned on, the sanding spindle assembly rotates and reciprocates (oscillates) up and down with respect to said worktable. This is referred to as the spindle sanding mode of operation of the sander.
In the '822 application, there is disclosed an additional feature of the sander, namely that it is constructed to facilitate conversion of the apparatus between a oscillating spindle sander and an oscillating belt sander.
When the sander disclosed in the '822 application and '507 patent is operated in spindle sander mode, a spindle sander assembly is attached to the output motor shaft, which reciprocates or oscillates up and down at a speed slower than it rotates. The dual rotary and oscillatory movement allows the sanding spindle to very efficiently remove material from a workpiece, without creating scratch patterns characteristic of conventional, i.e., non-oscillating, drum sanders.
When the sander disclosed in the '822 application is operated in belt sander mode, a belt/pulley system is attached to the output motor shaft. The belt/pulley system includes a drive drum and a driven drum about which a sanding belt is entwined. Both the drive drum and the driven drum reciprocate or oscillate as they rotate with respect to the worktable, carrying the belt with them, such that an oscillating or reciprocating belt sanding action is achieved.